When a control lever extending between the operator-side space and the device-side space is employed, and particularly, when the control lever is arranged to extend through an opening formed in the frame structure such as a floor panel, it is required to prevent dust from entering the operator-side space where the operator is present from the device-side space as much as possible.
According to Japanese Unexamined Patent Application Publication No. 2006-313396 and its similar Publication No. 2006-224840 disclosing a dustproof arrangement for the control lever in a tractor as an example of the work vehicle, the control lever is supported to a pivotal shaft that is mounted in a position distant from the frame structure downward to be oscillatable about the pivotal shaft, and an elongated opening is formed in the frame structure along the oscillating direction of the control lever. An elastic member made of rubber having a slit, through which the control lever extends, to cover the elongated opening and to allow the control lever to be oscillated. Further, a foamed plastic member such as a sponge that is elastically deformable is provided to lie over the elastic member, thereby to close the portion opened through the opening.
In this conventional arrangement, since the foamed plastic member that is elastically deformable is provided to lie over the elastic member, it is prevented that an inner edge of the elastic member where the opening is formed is turned up to produce a gap. On the other hand, since the control lever is moved and operated within the slit-like passage formed in the elastic member, a gap is produced in the member forwardly or rearwardly in the moving direction of the control lever as the control lever is oscillated, as a result of which dust may pass through the gap. Further, owing to the arrangement in which the control lever is freely inserted into both the elastic member and the foamed plastic member, an elastic restoring force of the elastic member or foamed plastic member in the position where the control lever penetrates is abated through a change over the years as the control lever is repeatedly oscillated for a long period of time. That may lead to formation of a gap.
Another control lever system is known from U.S. Pat. No. 4,610,179 in which the elastic member fills between the opening and the lever.
A further control lever system is known from US 2003/0033898 including a boss defining a pivotal axis for the control lever, a control lever portion extending to one direction from the boss, and a controlled lever portion extending to a different direction from the boss.